(CNN) -- Venezuelan authorities have captured two Colombian spies, says President Hugo Chavez, who also is accusing the United States of being behind efforts to destabilize his leftist government.

The Colombian Administrative Department of Security, known by its Spanish acronym DAS, denies any espionage against Venezuela.

Chavez said the two Colombians will be put on trial.

"When a hostile government increases its investigations, daring to violate international accords ... that indicates there are plans against Venezuela, and behind those Colombians is the hand of the CIA and the U.S.," Chavez said Tuesday. "Respect us like we respect Colombian sovereignty."

Francisco Arias Cardenas, the Venezuelan vice minister of foreign affairs for Latin America, said the government sent a protest note to the Colombian Foreign Ministry.

"DAS agents were captured spying, which violates the agreements of the Charter of Nations between brother countries, and we reject such actions," Arias Cardenas said Tuesday.

He said the Venezuelan Foreign Ministry demanded that the Colombian government "stop ... activities in Venezuelan territory that are not friendly or fraternal at all."

DAS Director Felipe Munoz said Wednesday the agency had not given any instructions to its agents to go to Venezuela. In fact, a separate DAS statement said, an internal order forbids agents from going to Venezuela under any circumstances.

Along with the denial, Colombia accused Venezuela of illegally holding a DAS officer.

The DAS said Detective Julio Enrique Tocora Parra was arrested September 29 while vacationing at Las Delicias Hotel in the Venezuelan city of Maracaibo, near the Colombian border. Tocora Parra had been invited there by a Venezuelan immigration official, Munoz said.

He said the department had not received any information about the agent's legal status or the reasons for his detention. And efforts by Colombian diplomats to visit the agent have been denied, the DAS said.

Both nations referred to the recent abduction and slaying of eight Colombians in a Venezuelan border town. The bodies were discovered Saturday and returned to Colombia on Tuesday. The men had been abducted October 11.

Venezuelan official Arias Cardenas said the arrest of the DAS agents had nothing to do with the slayings.

A DAS statement Tuesday said it had reiterated to Venezuela Colombia's concern about the killings and pledged to cooperate in the investigation.

Venezuela and Colombia have had long-standing problems, some having to do with the 45-year-old war between Colombia and the Marxist guerrilla group called the Revolutionary Armed Forces of Colombia, known as the FARC.

Venezuela is angry with Colombia for negotiating a treaty that will allow the United States to station personnel at seven Colombian military bases. Chavez says the United States wants the bases in neighboring Colombia to help topple his government. The United States says it needs the bases to help fight South American narcotics traffickers.